Elevated in more than 90% of people with primary hyperparathyroidism adding 0.8 mg/dL to the total calcium level for every 1 g/dL decrease of serum albumin below 4 g/dL; the corrected value determines whether true hypocalcemia is present. When calcium levels are reported as high or low, calculate the actual level of calcium by the following formula: Corrected total calcium (mg/dL) = (measured total calcium mg/dL) + 0.8 (4.4 - measured albumin g/dL)

Ionized calcium is approximately 46%-50% of circulating calcium and is the form of calcium available for enzymatic reactions and neuromuscular function; levels increase and decrease with blood pH levels; for every 0.1 pH decrease ionized calcium increases 1.5%-2.5%